The present invention is related to a power management system for use in connection with battery cells, which allow the cells and batteries to be turned into variable energy storage sources, which can be used in devices, such as for example, electric vehicles or grid storage. More specifically, the present invention is a platform, which uses a switch nodule having 2n+2 switches, where n is 1 or more and based upon the number of energy modules, and includes switch modules based upon inverted H-Bridge circuitry, as well as a switch module having an alternating polarity, which will be discussed further later, in combination with software which allows for real-time monitoring, management, control, and configuration of energy modules.
Battery-Powered Applications include either an AC-DC converter that converts an AC source such as a 120V, 60 Hz wall outlet, to the appropriate DC level to charge the battery, or a DC-DC converter to convert a DC power source such as a solar panel, to appropriate level to charge the battery pack. Battery powered applications also include a converter/inverter to provide power to the load application, where load may be either DC, such as a DC motor in an electric vehicle, or AC like an AC motor for a fan. The DC-AC inverter has to be adapted to compensate for voltage variations occurring in the DC supply voltage. Such voltage variations may occur due to discharging the battery cells during operation. Often, a DC-DC converter is connected between the battery arrangement and the DC-AC inverter. The DC-DC converter is adapted to provide a constant DC supply voltage to the DC-AC inverter, and therefore compensates for voltage variations in the voltage provided by the battery arrangement. Unfortunately, providing the DC-DC converter adds to the complexity of the system. DC-DC converters may also provide unnecessary power losses and/or additional overhead requirements in the balance of system.
The battery arrangement includes a number of battery cells, which are rechargeable cells, such as lithium-ion cells. These cells are connected such that they share a common ground. A number of battery cells are connected in series or parallel, where a DC charging voltage is provided by this series arrangement. High voltage batteries also may involve connections of many cells or cell modules for other purposes. For example, use of high voltage batteries include battery cell arrays for aerospace/spacecraft applications, telecommunication power supplies, computer power supplies, uninterruptible power supplies, electric utility energy storage, commercial applications, solar energy storage, wind energy storage, and the like. High voltage batteries may be of different types including lithium-ion cells, fuel cells, other electrochemical cells, and the like.
Also, most types of accumulator cells, such as lithium-ions cells, should not be discharged below a lower voltage limit or charged above a higher voltage limit, in order to prevent degradation or damage. In order to prevent improper discharging or charging of individual accumulator cells, cell-balancing schemes are applied. Such balancing schemes involve discharging more highly charged cells to the benefit of less charged cells, or in the case of charging, charging more lowly charged cells to the benefit of high charged cells. Circuit arrangements for performing cell balancing schemes are required in addition to the DC-AC inverter and charger.
It is very desirable to simplify battery management systems and to reduce aging and extend the life of battery cells as much as possible to reduce the cost of replacing the batteries. Further, there is a need in the art for a system to carefully control and optimize the re-charging of battery cells and any other electrical storage devices in a manner to mitigate damage during charging and extend the life of the storage device. Similarly, these same requirements apply to discharge and the interaction of both charging and discharging. Another concern associated with cell life and battery management systems is parasitic loss, internal discharge and unnecessary power level overheads required to serve certain applications.
In prior art systems, cell monitoring and balancing are achieved either by including complex electronic circuitry at each cell, or electrical connectors with many contacts to allow external circuitry to monitor and balance the cells. Complicated circuitry at each cell is inherently less reliable. If many connections are required, the connectors present electrical shock safety issues. If the connectors are heavy, then they may be unsuitable for aerospace, spacecraft, and other portable applications.
For some applications, it may be desirable to provide separate battery system components such as an external charger and an external cell charge measurement subsystem. To provide the capability to monitor individual battery cells, a multi-pin connector and additional wiring or sense lines on the battery is required. In large high voltage batteries, such a connector has several disadvantages. The connector needs at least one pin per cell. Since the battery can produce high voltages, the sense lines need a safety disconnect or electrical isolation to avoid exposing ground personnel or crew to high voltages when the connector is used. Since the battery can produce high currents, the sense lines may also need some sort of fusing or other wire protection as well.
Addressing safety concerns, regulatory compliance and emergency management procedures may also require additional monitoring, control and safety switches introducing additional componentry, failure points and cost.
Patents showing efforts to solve the problems with managing battery charging and systems include U.S. Pat. No. 7,148,654, issued Dec. 12, 2006, to Burany et al, which discloses a system and method for monitoring cell voltages for a plurality of electrochemical cells connected in series forming a cell stack. The method includes dividing the cells into at least two cell groups, measuring the voltage across each cell group and estimating the minimum cell voltage for each group based on the average cell stack voltage and an estimated number of deficient cells in each group. The lowest minimum cell voltage for the entire cell stack is then determined.
U.S. Pat. No. 7,081,737, issued Jul. 25, 2006, to Liu et al, discloses a monitoring circuit for monitoring a voltage level from each of a plurality of battery cells of a battery pack includes an analog to digital converter (ADC) and a processor. The ADC is configured to accept an analog voltage signal from each of the plurality of battery cells and convert each analog voltage signal to a digital signal representative of an accurate voltage level of each battery cell. The processor receives such signals and provides a safety alert signal based on at least one of the signals. The ADC resolution may be adjustable. A balancing circuit provides a balancing signal if at least two of the digital signals indicate a voltage difference between two cells is greater than a battery cell balance threshold. An electronic device including such monitoring and balancing circuits is also provided.
U.S. Pat. No. 6,983,212, issued Jan. 3, 2006, to Burns, discloses a battery management system for control of individual cells in a battery string. The battery management system includes a charger, a voltmeter, a selection circuit and a microprocessor. Under control of the microprocessor, the selection circuit connects each cell of the battery String to the charger and voltmeter. Information relating to battery performance is recorded and analyzed. The analysis depends upon the conditions under which the battery is operating. By monitoring the battery performance under different conditions, problems with individual cells can be determined and corrected.
U.S. Pat. No. 6,844,703, issued Jan. 18, 2005, to Canter, discloses a battery cell balancing system for a battery having a plurality of cells. The system includes a power supply and a plurality of transformer/rectifier circuits electrically coupled to the cells. Preferential charging occurs for a cell with the lowest state of charge. At least one current limiting device is electrically coupled to the transformer/rectifier circuits and the power supply. The current limiting device buffers a source voltage from a reflected voltage of at least one of the plurality of cells).
U.S. Pat. No. 6,803,678, issued Oct. 12, 2004, to Gottlieb et al, discloses a UPS system for providing backup power to a load and includes: a power input; multiple batteries; multiple battery housings, each containing one of the batteries, the batteries being coupled in parallel; multiple battery-monitor processors, each monitor being disposed in a respective one of the battery housings and coupled to the corresponding battery; a UPS processor coupled, and configured, to receive monitor data from the plurality of battery-monitor processors; a UPS-processor housing containing the UPS processor and being displaced from the battery housings; and a power output coupled and configured to selectively provide power from one of the power input and the batteries.
U.S. Pat. No. 6,664,762 issued Dec. 16, 2003, to Kutkut, discloses a battery charger for charging high voltage battery Strings that includes a DC-to-AC converter, which drives the primary of a transformer having multiple secondaries. Each secondary winding has a corresponding output stage formed of a rectification circuit, output inductor, and output capacitor. The output terminals of the output stages are connectable either in parallel or series. In either configuration, inductor current and capacitor voltage automatically balance among the output stage circuits. A controller normally regulates output terminal voltage by operating in voltage mode, but limits current by operating in a current mode when the average of inductor currents exceeds a specified limit. Reconfiguration from parallel to series, or vice versa, is obtained physical reconnection of the output stage terminals and adjustment of a single voltage feedback scaling factor. Connecting the output stages in series to produce a high voltage output reduces voltage stresses on the rectification circuits and enables use of Schottky diodes to avoid reverse recovery problems.
U.S. Pat. No. 6,583,603, issued Jun. 24, 2003, to Baldwin, discloses an apparatus and method for controllably charging and discharging individual battery cells or groups of battery cells in a string of batteries employed as a back-up power supply. The apparatus includes battery supply modules for at least partially isolating battery strings from the load bus and primary power supply. The partial isolation is effected by a switching network including two controlled switches arranged in parallel to selectively isolate the string of batteries. In certain disclosed embodiments, one of the controlled switches is turned on to connect the string of batteries to the load bus until the other controlled switch closes. The system includes a main power supply that supplies a power bus to a regulator in each battery supply module, which is used for charging the battery string, and a discharge bus to each battery supply module for discharging the batteries.
U.S. Pat. No. 6,268,711 issued Jul. 31, 2001, to Bearfield, discloses a battery manager that provides the ability to switch multiple batteries, battery cells, or other forms of power sources to power external devices individually, in series, and/or in parallel. The device is typically electronic based and consists of voltage level detecting circuits for comparing each power source to a reference voltage, FET control logic for controlling the switching matrix, and a switching matrix which accomplishes the required configuration of power sources to provide an output power source. The invention can be extended with the addition of an output power monitor, DC/DC converter, and control signals that augment internal switching. Depending upon implementation requirements, the battery manager can be in the form of a single integrated circuit.
U.S. Pat. No. 6,181,103 issued Jan. 30, 2001, to Chen, discloses a system converting a smart battery pack into a removable and data accessible (RADA) battery pack and an intelligent power management algorithm embedded in the host computer. The RADA battery pack contains a temperature sensor, a display unit, and a memory (EEPROM). Peripherals mounted on the host computer side contain a control unit, a charging circuit, a load circuit, a voltage divider, a current detector, a temperature control circuit, and a data bus are used to cope with the removal and data access operation for the AICPM system. The removable and data-accessible battery pack utilizes the functions provided by this invention to read, update, and record data about the battery pack, such as number of times used, remaining capacity, usable time, and nominal capacity. It also stores these data in the EEPROM of the RADA battery pack so that when the battery pack is used next time, the AICPM system can read out these data from the EEPROM and use them as the battery pack new information.
U.S. Pat. No. 6,031,354 issued Feb. 29, 2000, to Wiley et al, discloses an on-line battery management and monitoring system and method for monitoring a plurality of battery cells identifies and computes individual cell and battery bank operating parameters. The system comprises a central monitoring station to which a plurality of controllers is connected, each controller having a plurality of battery cells which it monitors. Features of the invention include the following: display of measurement and alarm condition data for each of the battery cells connected to each of the controllers; color-coded display of data for a battery cell, the display color being dependent upon the condition of the battery; performance of data analysis and initiation of necessary maintenance requests; operation of the controllers in an automatic local mode, automatic remote mode, or maintenance mode; provision for periodic calls from the controllers to the central monitoring station; and generation of red alarm calls, yellow alarm calls, downscale alarm calls, and diagnostic calls between the central monitoring station and the controllers.
U.S. Pat. No. 5,982,143, issued Nov. 9, 1999, to Stuart, discloses an electronic battery equalization circuit that equalizes the voltages of a plurality of series connected batteries in a battery pack. The current waveform is in the shape of a ramp for providing zero current switching. The transformer has a primary winding circuit and at least one secondary winding circuit. In one embodiment, each secondary winding circuit is connected to a different pair of batteries. The equalizing current is provided to the lowest voltage batteries in one-half of the battery pack during one-half of the charging cycle. The equalizing current is then provided to the lowest voltage batteries in the other half of the battery Pack during the other half of the charging cycle. In another embodiment, each secondary winding circuit is connected to a different single battery. The equalizing current is supplied to a lowest voltage battery in the battery pack during each half of the switching cycle. The electronic battery equalization circuit also includes a feedback control circuit coupled to the primary winding circuit for controlling the current from the equalizing current supply source. In another embodiment, optically coupled switches are connected to a battery voltage monitor to provide equalizing current to the lowest voltage even and odd numbered battery in the battery pack.
U.S. Pat. No. 5,923,148 issued Jul. 13, 1999, to Sideris et al, discloses an on-line battery monitoring system for monitoring a plurality of battery cells that identifies and computes individual cell and battery bank operating parameters. The system comprises a controller for designating a given battery cell to be monitored, a multiplexer responsive to designation by the controller for selecting a given battery cell to be monitored or for selecting a battery pack to be monitored, an analog board for receiving electrical signals from a given battery cell for providing an output representing measurement of a parameter (voltage, temperature, and the like) of the given battery cell, a voltage sensor circuit for sensing voltage appearing across positive and negative terminals of the battery pack, and a control board responsive to address information for selectively initiating a load test, battery bank charging, or common-mode voltage measurement.
U.S. Pat. No. 5,914,606 issued Jun. 22, 1999, to Becker-Irvin, discloses a circuit and method for making differential voltage measurements when one or both measurement points are at voltages that exceed those allowed by a typical differential amplifier, and is particularly useful for monitoring the individual cell voltages of a number of series-connected cells that make up a rechargeable battery in which some cell voltages must be measured in the presence of a high common mode voltage. Each measurement point is connected to an input of a respective voltage divider, with all the divider outputs connected to a multiplexer having two outputs. The two multiplexer outputs are connected to a differential amplifier. When the voltage dividers are “closely matched,” the output of the differential amplifier is directly proportional to the differential voltage between the pair of points to which the dividers are connected, and the differential voltage between those two points is accurately determined. The voltage dividers divide down the voltage of each measurement point so that each is low enough to be input to a conventional differential amplifier. By selecting the “ratio” of each voltage divider, the circuit can be used to measure differential voltages in the presence of almost any common mode voltage. The invention requires a single differential amplifier powered by a conventional dual power supply.
U.S. Pat. No. 5,666,040, issued Sep. 9, 1997 to Bourbeau, discloses a safe, low-cost battery monitor and control system. Electronic modules are connected to the terminals of respective batteries that make up a series string. Each module produces a go/no-go signal for each of four battery conditions: over-voltage, under-voltage, over-temperature and float-voltage, which are read by a network controller connected to each module via a single three-wire local area network. Based on the information received, the controller can adjust the charging current to the string, terminate the charge cycle, limit the current drawn from the string when in use, or disconnect the string from the system it is powering. The controller can record a history of the charge and discharge activity of each battery, so that the weakest batteries can be identified and replaced instead of scrapping the entire string. The system controls the charging current delivered to each battery during a charge cycle to insure that each battery is neither overcharged nor undercharged, by connecting a bypass circuit across the battery's terminals to reduce the charging current when an over-voltage condition is detected, or by reducing charge current to the String, A battery's voltage measurement is temperature compensated so that it can be accurately compared to temperature dependent limits. The addressable switch is bidirectional, so that the controller can, for example, force bypass resistors to be connected across selected batteries in order to heat up the batteries in a cold environment.
US Patent Publication 2007/0279003, published on Dec. 6, 2007, to Altemose et al, discloses a system for balancing charge between a plurality of storage battery cells within a storage battery. The battery balancing system sense changes, possibly caused by environmental influences, in the overall resonant frequency of charge balancing circuits contained within the battery balancing system. Using a phase locked loop based controller, the battery balancing system compensates for the change in resonant frequency by driving the battery balancing circuits at a frequency that matches the actual sensed resonant frequency of the battery balancing circuits.
U.S. Pat. No. 7,489,107 teaches a system and method for charging and extending the life of an electrical storage device and provides for developing a cell model structure of the electrical storage device, determining model parameters for charge-discharge data of the structure, by measuring voltage values of the structure based upon the charge-discharge behavior and deriving an instantaneous damage rate from the measured voltage values, and determining charge-discharge behavior of the structure in a voltage-charge plane to develop a charging profile based upon the instantaneous damage rate, so that the charging profile optimizes a charging current with respect to the damage per cycle. The system and method utilizes a hybrid model approach to extend the overall life of the electrical storage device.
US Patent Publication 2011/0198936 teaches a circuit arrangement including a multi-level converter. The multi-level converter includes: voltage supply terminals adapted to provide an AC output voltage; at least two converter units, each converter unit including input terminals adapted to have an electrical charge storage unit connected thereto, output terminals, and a switch arrangement connected between the input and the output terminals, the switch arrangement being adapted to receive a control signal, and being adapted to provide a pulse-width modulated output voltage having a duty cycle at the output terminals dependent on the control signal, the at least two converter units being connected in series with each other between the voltage supply terminals; and a control circuit adapted to generate the control signals for the at least two converter units such that the duty cycle of the output voltages of the at least two converter units is dependent on a desired frequency of the AC output voltage, and is dependent on at least one of a cycle parameter, or a charge state of the charge storage units.
U.S. Pat. No. 8,183,870 teaches a battery system utilizes a plurality of transformers interconnected with the battery cells. The transformers each have at least one transformer core operable for magnetization in at least a first magnetic state with a magnetic flux in a first direction and a second magnetic state with a magnetic flux in a second direction. The transformer cores retain the first magnetic state and the second magnetic state without current flow through said plurality of transformers. Circuitry is utilized for switching a selected transformer core between the first and second magnetic states to sense voltage and/or balance particular cells or particular banks of cells.
In battery-powered applications there has been a recent effort to utilize an inverted H-Bridge structure for the purpose of battery management and charging. For example, U.S. Pat. No. 4,467,407 to Asano et al. teaches a multi-level inverter topology where the multi-level inverter comprised of a group of DC power supplies including 3 or more which are connected in series, including a plurality of terminals for taking desired voltage levels, and a group of switches whereby a contact of a switch connected to a terminal corresponding to the desired voltage level is closed to output voltages at multi-levels to a load. The Asano system also includes a control circuit, and provides a method by which may provide a voltage to a multi-phase load.
U.S. Pat. No. 5,642,275 to Peng, et al. teaches a multilevel-cascaded voltage source inverter with multiple DC sources whereby the inverter is applicable to high voltage applications. This inverter consists of at least one phase, where each phase has a plurality of full bridge inverters with an independent DC source (i.e. a battery), where the inverter develops a near-sinusoidal approximations, and the inverter has been designed specifically for applications in voltage balancing and compensating reactive power.
U.S. Pat. No. 8,330,419 to Kim et al. teaches a dynamically reconfigurable framework for management of large-scale battery systems. This framework functions on a set of rules that govern how battery cells should be used or bypassed to recover from cell failures. Kim discusses a constant-voltage-keeping policy and a dynamic-voltage-allowing policy that supplies power to various applications, which focuses on voltage output requirements, as well as isolating/removing a cell from the battery string.
U.S. Pat. No. 8,508,191 to Kim et al. discusses a system for charge scheduling in batteries for the purpose of extending battery life by dynamically adapting battery activity based on battery health and load demand. This patent proposes a filtering technique whereby load demand is handled, and a “scheduler” which allows batteries to be charged and discharged simultaneously. Kim is focused on the separation of a battery pack into a section, which may be charged, and a section which may be discharged. To accomplish this, Kim proposes a method for determining the SOC of a battery, and provides a filtering method. The proposed invention, although also proposes a method of detecting the SOC of a battery and using that to determine if a given cell can be used, and goes further by stating applications of load control, scaling, and charging-source flexibility (i.e. AC/DC). The proposed method also discusses fault detection and mitigation, which is not included in this work.
US Pat. Publication No. 2011/0198936 to Graovac et al. discloses a circuit arrangement including a multi-level converter for use in application where an AC motors is required to be driven by a DC source, such as a battery pack. It proposes a method of using the multi-level converter topology to construct an AC sine wave similar to U.S. Pat. No. 5,642,275 to Peng, et al., which focuses on the application of the well-known multi-level converter bridge topology to provide AC voltage to a load by commanding localized switches on the energy storage device. US Pat. Publ. No. 2011/0267005 to Gollob et al. teaches an active charge balancing circuit and energy storage arrangement methods based on a combined electrical switch topology and associated control circuitry to control the switches such that a given cell may be bypassed, or the flow current may be reversed in a given collection of cells.
It would be desirable to provide a battery and/or cell monitoring and management system with minimal complexity such as the absence of need for fusing on sense lines, electrical isolation for each cell, limited leakage current drains on the cells, and limits to overcharge rates for the individual battery cells.